1. Field of the Invention
The present invention relates to a recording medium.
2. Description of the Related Art
Recording media including ink-receiving layers on substrates are known as recording media on which recording is performed by ink jet recording methods or with felt-tip pens. Ink-receiving layers contain inorganic pigments, such as silica and hydrated alumina, and binders, such as polyvinyl alcohols. Such recording media are required to have improved ink absorbency, moisture resistance, ozone resistance, and so forth. In the case where dispersions are used as coating liquids for forming ink-receiving layers and where ink-receiving layers are formed by applying coating liquids on substrates, inorganic pigments are required to be satisfactorily dispersed in dispersions.
Japanese Patent No. 3791039 discloses an alumina sol containing hydrated alumina and a deflocculant. As the deflocculant, a sulfonic acid that does not have a carbon atom, e.g., sulfamic acid, an alkylsulfonic acid having 5 or more carbon atoms, e.g., hexanesulfonic acid, a sulfonic acid having a benzene ring, or the like is used. Japanese Patent No. 3791039 also discloses that an alumina dispersion has a solid content of 15% to 30% by weight and an ink-receiving layer to be formed has satisfactory absorbency.
Japanese Patent Laid-Open No. 2001-260519 discloses a recording medium having satisfactory ink absorbency, preservability, and gloss, the recording medium including an ink-receiving layer that contains silica and one compound selected from sulfinic acid compounds, thiosulfonic acid compounds, and thiosulfinic acid compounds.